This invention relates generally to restricting access to content information, such as video data, audio data, etc. and in particular to a method and apparatus for restricting privilege access to distributed content information.
Computers are known to include a central processing unit, system memory, audio processing circuitry, video processing circuitry, and peripheral ports such that the central processing units may interface with peripheral devices such as printers, monitors, external tape drives, etc. The video graphics circuit is a co-processor to the central processing unit and performs the co-processing function of preparing data for display on a computer monitor. The video processing circuitry receives graphics data from the central processing unit and converts the graphics data into pixel information for display on the monitor.
The video processing circuit may further process video data that is received via television broadcasts, cable broadcasts, satellite broadcasts, signals from VCRs, and signals from DVD players. To receive such signals, the video processing circuit includes a tuner circuit, an audio decoder and a video decoder. The tuner is operably coupled to receive the broadcast signals and to convert them in to digitized audio signals and digitized video signals. The audio decoder receives the digitized audio signals and converts them into analog signals that are subsequently rendered audible. The video decoder receives the digitized video signals and converts them into video graphics data, which can be displayed on a display (e.g., a computer monitor, TV, etc.). As is known, the video graphics data is in a form that can be stored by the computer""s system memory. As such, a computer user may record a television broadcast, cable broadcast, satellite broadcast, VCR transmission, or DVD transmission in the computer""s memory for later replay.
Needless to say, content providers (e.g., Hollywood movie makers, television program makers, and distributors) are concerned about unauthorized copying or viewing of their video content. To help reduce the casual copying of such video content, several techniques have been developed. For example, video cassette tapes include an embedded coding that degrades VCR generated copies, but does not affect the display of the original video content on a television. As a further example, digital video discs (DVD), which are digitally recorded, include an embedded copy restriction flag, or a serial copy generation management system (CGMS), in the digital video signals, i.e., the output of a DVD player. The CGMS information indicates, for the entire disk or sectors thereof, whether no copies, one copy, or unlimited copies can be made. As is generally understood, for the copy prevention to work, equipment capable of making copies needs to abide by the copy restriction rules.
While the DVD player, which may be incorporated in a computing system, prevents copying of the video content in accordance with the copy restriction flag, the monitor receives unprotected video graphics data via a standard analog VGA link or digital differential signaling (such as: TMDS [transition minimized differential signaling]; LVDS [low voltage differential signaling] or GVIF [graphics video interface] link. As such, a person intent on obtaining an unauthorized copy of the video content may obtain a VGA or digital differential signaling converter and record or view the video content from the VGA output. One contemplated solution for overcoming copying or viewing from the video graphics controller output is to encrypt the video graphics data provided on the VGA or digital video signaling link. As is also known, the more complex the encryption algorithm, the less likely it is to be broken, but the more it costs. Thus, a computer equipment manufacturer may be left with a difficult choice of including less expensive encryption protection, which can be readily broken by a computer hack, or include more costly encryption protection, which provides the desired security, but may price their equipment out of the market.
A further copy restriction issue arises when a user, who obtained a DVD in an authorized manner (i.e., purchase or lease), is unable to play the DVD. A DVD may not be played if the DVD does not include a copy restriction flag. As is known, some DVD players are designed to check for a copy restriction flag. If copy restriction flag is not found, the disk is presumed to be an illegal copy and is not played. The user, however, is not informed as to why the disk is not playing. This is problematic for a user who believes that he or she obtained a valid disk and does not know why it is not playing. Thus, the user does not know whether his or her equipment is damaged, the disk is damaged, or the copy is an illegal copy and not authorized to be played. A user would further benefit from being informed as to the copying restriction status of valid discs.
Therefore, a need exists for a method and apparatus that prevent unauthorized copying or viewing of distributed content information without expensive encryption techniques and inform users of copy restrictions regarding the distributed content information.